Uno: Button with Text does not correctly show on Android

[TonyHenrique]

I put a simple

<Button>OK</Button>

But on Android it only renders the Button, without the Text
On UWP, it renders OK.

If I change to

<Button><TextBlock>OK</TextBlock></Button>

Then it renders correctly on Both.

[jeromelaban]

The ContentProperty attribute's behavior in the source generator is incorrect for implicit string content.

This will soon be fixed.

Thanks!

[jeromelaban]

Fixed as part of #43